Rigid segmented flexible anchors

ABSTRACT

An prosthetic implant replaces hyaline cartilage in a synovial joint with a flexible polymer sliding surface, preferably of hydrogel, on a segmented support with an array of adjacent segments to which the hydrogel is molded. Adjacent segments are laterally and angularly displaceable permitting the implant to conform to rounded or irregular surfaces or to be rolled or folded for arthroscopic placement. Tension cables threaded through segments along a circuit can cinch segments together for stiffening the supporting layer and/or the cable can pull the implant against a bone surface. Adjacent segments can have inter-engaged structures. In some embodiments the segments are carried on a flexible foil or fibrous sheet.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. provisional applicationSer. 62/101,402, filed Jan. 9, 2015, the disclosure of which is herebyincorporated by reference in its entirety.

BACKGROUND Field of the Invention

This invention concerns prosthetic surgical implants for replacing orsupplementing hyaline cartilage in articulating joints. Moreparticularly, implants with plural layers are structured to includelaterally adjacent segments permitting relative angular displacementwhereby the implant can flex and/or conform to a surface that is curvedin orthogonal planes. The opposite faces of the implant have abone-facing layer on one side, adapted to support tissue ingrowth, and alubricious hydrogel sliding layer on the opposite side. The segments canbe coupled and supported by lines extending through passages (cannulae)in adjacent segments, permitting flexing of the implant along hingingaxes. The lines can be anchored and tension on the lines can alter theshape of the implant by application of pressure between segments.

Relevant Art

US Patent Application 2007/0224238, which hereby is incorporated in thisdisclosure by reference, in its entirety, explains that hyalinecartilage is the main type of cartilage that provides smooth, slippery,lubricated surfaces that slide over and rub against other cartilagesurfaces in “articulating” joints, such as knees, hips, shoulders, etc.Natural hyaline cartilage forms as a relatively thin layer (usually nomore than about 3 or 4 millimeters thick) that covers certain surfacesof hard bones. While the hyaline cartilage in some joints (such asfingers) is not heavily stressed, the hyaline cartilage in other joints(notably including knees and hips) is frequently and repeatedlysubjected to relatively heavy compressive loads, shear forces, and otherstresses. Such cartilage does not have a blood supply or cellularstructure that enables the type of cell turnover and replacement thatoccurs in most other tissues. As a result of those and other factors,hyaline cartilage in knees and hips may need repair or prostheticreplacement at fairly high rates among the elderly (due to gradual wear,injury, disorders such as osteoarthritis or rheumatoid arthritis, etc.),and at lower but considerable rates among younger patients (due toinjury, congenital joint displacements that lead to unusual wearpatterns, etc.).

The present invention relates to certain specific techniques andstructural designs for anchoring layers for carrying hydrogel componentsof implants. Natural hyaline cartilage is present only in relativelythin layers that coat the surfaces of bones and are diffused into thebone tissue for affixation. For emulating hyaline cartilage in anarticulating joint, the rigid segmented flexible anchoring layers thatcarry hydrogel, as disclosed herein, are likewise configured to be thin.

Most hydrogels that have substantial tensile strength (which are theonly hydrogels of interest herein) hold water molecules within acohesive polymeric molecular matrix, in a way that enables migration anddiffusion of the water molecules through the molecular matrix. Althoughsuch hydrogel materials have at least some degree of deformability forpurposes of elasticity, they cannot be in liquid form, i.e., theyadvantageously return to a specific undeformed shape after loads orstresses have been removed.

In natural cartilage, the hydrogel structure is created by athree-dimensional matrix that is given shape and strength mainly bycollagen. Collagen is a fibrous protein that holds together nearly allsoft tissues in animals. In synthetic hydrogels, the three-dimensionalmatrix usually has a molecular structure made of complex polymers thathave a combination of: (i) long continuous chains (often called“backbone” chains), containing mainly carbon atoms and sometimescontaining oxygen, nitrogen, sulfur, or other atoms as well; (ii) sidechains, which branch off the “backbone” chains in ways that can haveeither regular or semi-random spacing, length, content, etc.; and, (iii)crosslinking bonds, which connect the backbone and side chains to eachother in ways that create complex three dimensional molecules that havesufficient spacing between them to allow water molecules to travelwithin the molecular matrix. In natural cartilage, at the bone cartilageinterface there is a zone of cartilage calcification, at the tidal zone,where cartilage is calcified with collagen fibers extending across thetidal zone from the calcified cartilage to the softer cartilage.

Synthetic hydrogel polymers advantageously are hydrophilic, i.e.,composed to attract and hold water molecules. This can be accomplishedby including large numbers of oxygen atoms (usually in hydroxy groups),nitrogen atoms, or other non-carbon atoms in the backbone and/or sidechains, to provide “polar” groups that will attract water, a polarmolecule.

Fluid permeability (which involves the ability of water to pass throughthe molecular matrix of cartilage) is important in the behavior andperformance of natural cartilage. As an example, U.S. Pat. No. 6,530,956(also hereby incorporated by reference) illustrates at FIG. 6 how fluidflow through cartilage can help distribute stresses and pressures thatare imposed on cartilage in a load-bearing joint such as a knee, when aperson is walking or running.

For the purposes of this invention, synthetic hydrogel polymers areadvantageously flexible, and can be rolled into cylindrical forms thatcan be inserted into a joint that is being surgically repaired, via aminimally invasive incision, using an arthroscopic insertion tube. Byavoiding and eliminating the need for “open joint” surgery, arthroscopicinsertion of a flexible implant in a rolled-up cylindrical form canspare surrounding tissues and blood vessels from more severe damageduring an open joint surgical operation.

Due to these and other factors, hydrogel materials are of interest injoint repair implants, and may be able to provide better performancethan the solid plastics, such as ultra-high molecular weightpolyethylene (“UHMWPE”) that are used today in most hip and kneereplacements.

The recent and ongoing efforts to provide improved hydrogel implants forreplacing cartilage in joints by Mansmann (the inventor herein) aredescribed in U.S. Pat. No. 6,629,997 (“Meniscus-type implant withhydrogel surface reinforced by three-dimensional mesh”) and publishedapplications US 2002-0173855 (“Cartilage repair implant with softbearing surface and flexible anchoring device”), US 2002-0183845(“Multi-perforated non-planar device for anchoring cartilage implantsand high-gradient interfaces”), US 2004-0133275 (“Implants for replacingcartilage, with negatively-charged hydrogel surfaces and flexible matrixreinforcement”), all of which are hereby incorporated by reference, asthough fully set forth herein.

A bone surface that is covered by a layer of hyaline cartilage isreferred to herein as a “condyle.” However, it should be noted that thisterm is not always used consistently, by physicians and researchers.Some users limit “condyles” to the rounded ends of elongated bones. Thisusage includes the long bones in the arms and legs; it usually but notalways includes smaller elongated bones in the hands, fingers, feet, andtoes; and it normally excludes the cartilage-covered “sockets” in theball-and-socket joints of the hips and shoulders (while encompassing thecomplementary ball ends of the other bone that fits such a socket). Bycontrast, other authors use “condyle” to refer to any bone surfacecovered by hyaline cartilage, including the socket surfaces in hip andshoulder joints. Since reinforced hydrogels as disclosed herein can beused to replace hyaline cartilage segments on any bone surface, thebroader definition (which covers any bone surface covered by hyalinecartilage, including long bones, finger joints, socket surfaces in hipsand shoulders, etc.) is used herein unless specifically excluded in thedescription or its context.

A condylar surface (i.e., a hyaline cartilage-carrying bone surface)contains a transition zone, called the subchondral layer or zone, at theinterface between the hard bone and the cartilage. This transition zonestrengthens and reinforces the cartilage, ensuring that the cartilage(which is relatively soft) is not readily pushed or scraped off thesupporting bone when a joint is subjected to loading and shearingstresses. In the transition zone, large numbers of microscopic collagenfibers, firmly anchored in the hard bone, emerge from the bone in anorientation that is generally perpendicular to the bone surface at thatlocation.

When rounded surfaces are involved, a direction normal to the surfacemay be called radial; the surface-parallel direction at any point on arounded surface is called tangential. For convenience, the descriptionsand drawings herein typically assume a cross section wherein a bonesurface is positioned horizontally, with a layer of cartilage restingabove it and on top of it, and with the smooth articulating surface ofthe cartilage as the upper exposed surface of the structure. Thisorientation is for convenience of description, often with reference toan illustration. Unless otherwise stated, adjectives such as up/down,over/under, above/below and similar limitations should be taken asreferring to an arrangement wherein the bone is assumed to be the baseor lower tissue unless otherwise described, or according to a depictionin the drawings, and should not be regarded as limiting features of thesubject invention. The joint might be oriented in any direction at agiven time.

Bone is a relatively rigid biological material compared to cartilage.There are different typical rigidities of bones in the functionalskeleton, corresponding to a large extent to the mechanical demands ofthe segment of bone, as outlined by Wolff's Law. Subchondral bone, thebone directly adherent to a cartilage layer at the joint surface, iscomprised of a thin dense layer of bone. Less dense woven bone supportsthe subchondral joint articular surface. Dense cortical bone is found inthe long bones for structural support.

To employ soft hydrogel in an implant to replace damaged cartilage, itis advantageous to anchor the hydrogel to the associated bonearticulating surface in such a way as to promote healing of the hydrogelimplant to the bone recipient site, i.e., to secure the implant thatcarries the hydrogel surface exposed for sliding articulation. There isa significant modulus of elasticity mismatch in structuralcharacteristics between the cartilage, with relatively soft fragilematerial properties, and the subchondral bone, with relatively toughrigid material properties. This material modulus mismatch is well known.See, e.g., Rockwood & Green's Fractures in Adults, 6th Edition, 2006Lippincott Williams & Wilkins.

SUMMARY

The present developments concern continuing work based upon mechanical,tribological and pilot animal data, to develop hydrogel-basedtherapeutic devices and techniques that improve treatment optionsavailable for progressive osteoarthritis (OA) and post-traumaticosteoarthritis (PTOA). An object is to repair irreversibly damagedarticular bearing surfaces so as to improve function and reduce theprogression, pain, suffering, care and expenses associated witharthritis.

OA/PTOA can impact any joint, with variable disability impact. AlthoughPTOA differs from OA in etiology, age of onset, associated pathologiesand index injury treatment focus, both conditions can result inextensive damage to articular cartilage. Once damage to articularcartilage occurs, conservative management (e.g., anti-inflammatorydrugs, braces and visco-supplementation) has only marginal temporizing,palliative success. There are currently no successful, minimallyinvasive interventions in use for early end stage, bone on bone, jointpathologies that predictably forestall or possibly wholly avert the needfor total joint replacement (TJR) or joint arthrodesis (JA).Conventionally, TJR is the definitive procedure for OA/PTOA of the hip,knee and shoulder while joint fusion (JA) is an acceptable alternativefor smaller synovial joints and as salvage, last resort alternative forcomplications of the shoulder, hip or knee. Though a very successfulprocedure, TJR is associated with an open surgical approach, completereplacement of the natural joint, and typically requires a significanthospitalization with post-surgery rehabilitation.

It would be quite advantageous to provide “pre-arthroplasty”interventions that do not require an open joint approach, extensivehospitalization and prolonged recovery and rehabilitation times, forboth military and public needs. It is an object of the presentdisclosure to prosthetically resurface synovial bone-on-bone synovialjoints, using structurally supported hydrogel configured for attachmentto a bone by arthroscopic techniques. More generally, the inventionseeks to correct cartilage pathologies before progressive bone erosioncauses joint deformities indicating that more drastic treatment isnecessary.

This disclosure concerns improved anchoring systems joint for replacingdamaged cartilage in synovial joints. These implants are flexible, dueto segmentation of the implants for delivery into the joint. In additionthese devices are designed with an integral cable to be tensioned andthereby compressing the individual rigid segments together, to restorerigidity as the implant is installed and fixed to bone. The indicationsfor use centers around the treatment of painful osteoarthritic synovialjoints, for instance with bone on bone pathology secondary to damagedcartilage. These devices are designed for installation through anarthrotomy, arthroscopically assisted mini-arthrotomy or arthroscopy.

According to the present disclosure, a flexible conforming medicaldevice, is structured with laterally adjacent coupled segments, enablingthe device to be folded or rolled and delivered into an arthritic jointthrough a minimal incision. The device can be opened on the jointsurface with a lubricious hydrogel material on one side facing towardthe opposed bone. The opposite side can be configured for bone ingrowthand/or to be anchored using fasteners. The segments form a flexiblesheet structure.

In certain embodiments, the segments are connected to one another usingaligned passageways receiving tensioning lines or cables. The alignedpassageways can include edge mounted interlocking hinge parts onadjacent segments such that the adjacent segments can flex around anaxis defined by the line or cable extending through the passageways.

In certain embodiments the flexing around axes defined by parallelspaced tension lines is configured to permit the implant to be folded orrolled into a tube for delivery through a small incision in anarthroscopic procedure. Upon introduction, the implant is placed at therequired site. In certain embodiments, tension applied to the lines orcables can draw together the segments due to the path of lines or cablesaround a circuit or otherwise between end points at which the line orcable can be terminated at a connection to a segment or by anchoring toa fastener embedded in bone.

An array of segments can be coupled by membranes, foil, hinges or cablesin respective embodiments, and can be delivered and secured to the boneyrecipient site, thereafter contributing implant rigidity for goodfunctional performance, a stabilization in position for tissue healingand potential tissue ingrowth.

These and other objects are achieved in an implant for replacing hyalinecartilage in a synovial joint, the implant having a flexible polymersliding surface, preferably of hydrogel, on a supporting layer that issegmented. More particularly, the supporting layer has an array oflaterally adjacent rigid segments to which the hydrogel is molded. Thesegments are displaceable at least angularly relative to one another,such that the implant can flexibly conform to rounded or irregularsurfaces. The implant can be rolled up or folded for arthroscopicintroduction into the joint, after which the implant is placed andanchored to associated bone. The segments can be regular polygons, forexample. Alternatively, the implant can be segmented in a manner that iscustomized to the topography of the bone surface, for example withjunctions between segments aligned perpendicular to curvature gradientssuch that the implant can rest against rounded surfaces especiallyincluding the condoyles at the ends of articulating bones.

In some embodiments, cables are threaded through the segments andfacilitate anchoring to a bone. Tension applied to a cable extendingaround a circuit and intersecting plural segments can pull theintersected segments together or cinch the encircled segments together,for stiffening the supporting layer. The cable can be anchored atfasteners along the circuit and also anchored at end points that arebeyond edges of an implant wrapped over a rounded bone surface such thattension pulls the segments of the implant down against the roundedsurface. Adjacent segments can have complementary nesting shapes thathold a relative orientation when the segments are pulled into abutment,such as relatively inclined surfaces.

In certain embodiments, the segments are discrete elements but areaffixed to one another in a flexible or hinging manner where adjacentsegments abut. In an embodiment using cables, adjacent segments can haveinter-engaged hinge knuckles such that a cable through the knucklesfunctions as a hinge pin as well as an anchoring or tensioning element.This cable can be routed so as to provide hinging lines along which thesegments are flexibly inclined relative to a flat plane to wrap over acurvature.

An object of this invention is to provide improved methods of stablesecure fixation of a soft polymer or hydrogel bearing surface to arelatively rigid bone recipient site establishing a modulus ofelasticity gradient from the rigid bone to the compliant bearingsurface, resulting in a stable replacement device for damaged cartilagein an arthritic joint.

Another object is to provide a practical method of dividing a rigidstructure into plural individual rigid segments, thereby creating aflexible device to facilitate the delivery of the device through aminimal opening, to the desired site of function.

A further object is to achieve a method to restore these flexiblyassociated individually rigid segments into a rigid whole device, inparticular by applying tension via a tensioning line that draws thesegments into lateral abutment.

In certain embodiments, the implants are arbitrarily sized and comprisean array of regularly shaped segments from which a required anatomicalshape is approximated and cut out. In other embodiments, an implant thatis shaped to accommodate the installation site is subdivided to formsegments that can be angularly diverted from one another and arrangedloosely or drawn laterally together. An anatomically shaped implant thuscan be subdivided by strategic serpentine cutting into plural segments,along lines at which the rigid segments are hinged together permittingthe device to be flexed. Flexing can allow the implant to the rolled orfolded for delivery into the joint and then opened and restored to fullsize. The subdividing lines between segments advantageously complementthe contour of the installation site, for example with dividing linesoriented perpendicular to surface curvature gradients, such that thesegmented implant fits closely against the surface. As so fitted,implant rigidity is then achieved by tensioning of one or more cablestraversing the implant, during the installation anchoring procedures.

Another object of the invention is to provide a flexible sandwichhoneycomb segmented structure that can be flexed and delivered through asmall opening and then restored to its larger functional geometric shapeand internally tensioned into a rigid honeycomb structure.

Among other embodiments, a flexible sheet is provided as a carrier ofthe segments, for example comprising a woven or nonwoven fiber or aflexible thin metallic foil as a binding membrane on one side of therigid segments, thereby controlling the alignment, orientation andconfiguration of the implant in a flexible state and the accommodatingmovement into a final, tensioned, compressed rigid state of the device.

A method for securing an implant employs quilted mesh, having increasedloft for compression, by a tensioned suture grid, to relieve tensionstress at the polymer mesh interface of a relatively soft polymer orhydrogel bearing surface to a relatively rigid bone recipient site forreplacement of damaged cartilage in an arthritic joint.

These and other objects of the invention will become more apparentthrough the following summary, drawings, and description of thepreferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings illustrate certain nonlimiting embodiments fordemonstrating aspects of the invention, and wherein:

FIGS. 1A and 1B are the anterior and lateral views of a human knee modelshowing articulating ends of the femur and tibia with hydrogel implantssupplementing or supplanting medial and lateral articular cartilage atthe tibial plateau, the femoral condoyles and the menisci.

FIGS. 2A, 2B and 2C are views from different perspectives showing theimplants seen in FIG. 1A apart from the associated bones.

FIG. 3A is a plan view showing a structurally supportive component thatcan be provided in an implant, wherein certain segments (shown ashexagons) are joined to other segments at lines of lateral abutment, andgroups of joined segments provide pathways in which tensioning cablesare provided for drawing the groups of segments inwardly. FIG. 3B is aperspective view corresponding to FIG. 3A wherein the groups of segmentsare drawn inwardly into lateral abutment in a flat plane.

FIGS. 4A and 4B are respectively perspective and elevation views showingan embodiment as in FIG. 3B except that bilateral groups of the segmentsare pulled by the tension lines to hinge, pulling the bilateral groupsinto an alternative cup shaped contour.

FIGS. 5A and 5B are examples of orthopedic cerclage cable crimp andfixation devices of a type useful to affix tension cables as described.

FIGS. 6A and 6B are plan and elevation views of an individual segmenthaving an open frame structure with laterally protruding frame ends, anda regular polygon shape in plan.

FIG. 6C is a plan view of an array of polygonal segments as in FIGS.6A/6B, wherein the laterally protruding frame ends of adjacent segmentsare continuously joined in a lattice that is conformable to a nonplanarsurface at least to the extent of bending of the lateral frameconnections between segments.

FIGS. 7A, 7B and 7C are perspective views of a polygonal segment as inFIG. 6A except with complementary alignable hinge forming elements thatreceive tension cables.

FIG. 8 is a plan view showing an array of polygonal segments with hingeforming elements in frictional engagement with one another (i.e.,without inserted tension cables shown).

FIG. 9 is a schematic view showing one polygonal segment with hingingaxes that are selectable by running a tension cable through at least twoadjacent segments in the array of polygonal segments, being shown bydashed lines.

FIGS. 10A and 10B are respectively a plan view and a side elevation ofan alternative segment with fewer axes than in FIG. 9, and includingintegrally formed protrusions on the underside of the segment forinteracting with existing natural cartilage and/or bone.

FIG. 11 is a plan view of a segment array as in FIG. 8, with a tensioncable laced in a circuit through outer members of the array wherebytension on the cable draws the segments inward.

FIG. 12 is a perspective view illustrating an arrangement wherein atension cable laced through an array include depending loops arranged tointersect or loop around fasteners (not shown) for pulling the segmentsof an array down onto a bone surface as well as inwardly.

FIGS. 13 and 14 are elevation view showing adjacent segments withchamfered edge faces that when abutted form an angular diversion foraccommodating part of a curved surface.

FIGS. 15-17 are illustration of segments formed of elongated membersarranged as legs and struts, FIG. 16 showing an alternative for achamfered edge and FIG. 17 showing an edge nesting structure.

FIGS. 18A-18C show several exemplary types of trabecular and reticulatedmaterials with porous structure that facilitate tissue ingrowth.

FIGS. 19A-C are plan, elevation and underside-perspective views of analternative embodiment of a polygonal segment.

FIGS. 20A-D are elevation and perspective views showing forms ofsegments affixed to a backer sheet, in this case the segments comprisingcompressible quilted pad areas.

FIGS. 21A-C are detail views of a quilted pad embodiment as in FIGS.20A-D, with FIG. 21C showing a sectional view.

FIGS. 22A and B show additional quilted pad embodiments, wherein FIG.22B also shows a composite molded structure having an upper exposedlayer of hydrogel.

FIG. 23A shows a surgical grid that in FIG. 23B is laid over a segmentedbacker sheet. FIG. 23C show the composite molding of the backer sheet,surgical grid and hydrogel surface layer.

FIG. 24A is a schematic showing the stacking of a rigid-segment flexiblearray on a backer sheet. FIGS. 24B-D are details of an embodimentwherein separate segments have domed tops and are composite molded witha hydrogel surface layer.

FIG. 25A-D are perspective and plan views of an alternative embodimentof a rigid segment for use in an array, in particular having a domed topwith lateral macro-pores into which hydrogel protrudes in a compositemolding.

FIGS. 26A through C show a rigid-segment flexible array using segmentsas in FIGS. 25A-D; and FIG. 26D is a side elevation showing a compositemolding with hydrogel.

FIGS. 27A-E illustrate an alternative embodiment of rigid segments,especially for digital incremental production (3-D printing) andcharacterized by arching struts that flexible affix adjacent segments inFIGS. 27B-E and in FIG. 27E are embedded in the hydrogel surface layerof a composite molding.

FIGS. 28A-B illustrate a backer sheet, for example of metal foil; andFIG. 29A shows affixation of a rigid-segment array to the backer sheet;whereas FIG. 29B shows that array and backer in a composite molding witha hydrogel surface.

FIGS. 30A-B show an implant with a rigid-segment array on a backer sheetwith a tension cable in place for cinching together and anchoring theimplant. FIGS. 30C-D show an alternative embodiment with roundedperimeter segments and FIGS. 30E-F are details from FIGS. 30C-D.

FIGS. 31A-D are perspective and plan views juxtaposing bone anchors withan implant according to the previously described embodiments.

FIGS. 32-34 illustrate aspect of routing tension cables through segmentsof which strategically placed segments are anchored.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

According to the invention, sheet-like prosthetic implants replacecartilage in articulating joints, namely joints wherein synovial fluidlubricates the relative sliding of surfaces on articulating bones, whichsurfaces are arranged to slide over one another. Such joints are foundin the limbs of mammals such as the knees and shoulders of humans, andare distinct from joints that do not involve sliding surfaces such asintervertebral joints.

In the illustration of the internal elements of the human knee shown inFIGS. 1A, 1B, the bones articulate such that as the femur and tibiabecome inclined relative to one another at different angles, the hyalinecartilage that naturally occurs on the ends of these bones, namely onthe medial and lateral condoyles at the end of the femur and at the topof the tibia, slide relative to one another and relative to themeniscus, an intervening portion of cartilage that also bearscompression while facilitating sliding contact.

It is an aspect of this disclosure that prosthetic implants are providedto wholly or partly replace the natural cartilage elements, and theprosthetic elements comprise sheets configured as adjacent segments.

The segments are displaceable relative to one another in certain waysdescribed herein for conforming to the topography where the segments aredeployed, such as to wrap over a convex bone surface or to fit into aconcavity.

The segments carry a hydrogel lubricious sliding layer on at least oneside. In the case of the femoral and tibial cartilage implants thatemulate hyaline cartilage natural ingrown with the bone surface, theopposite side from the hydrogel has aspects that facilitate affixationto the bone surface, preferably including anchoring and optionallyconfigured to encourage tissue ingrowth. In the case of the meniscalcartilage implants that emulate a meniscus that naturally is attached toadjacent tissues in the joint capsule, both sides of the implant carryhydrogel lubricious sliding layers. Supporting structures such as areinforcing rib can wrap around each meniscal implant to ends that areanchored in the tibia to keep the implant stationary between the femurand tibia.

FIGS. 1A, 1B show a knee joint with hyaline and meniscal cartilageimplants in place, in anterior and lateral side elevation views. FIG. 2Ashows the implant cartilage configurations separately from the bones.FIGS. 2B, 2C show the implant cartilage elements for one condoyle fromdifferent orientations. It is apparent in these views that the implantsare generally sheet-like but the sheet curves over rounded bonesurfaces. The implants cover the contour of curved bone surfaces thatanatomically are capable of coming into sliding contact with the opposedbone at some position within the range of articulation of the joint.

According to the present disclosure, at least the implants elements thatcover curved condoyle surfaces are segmented. Segmentation of theimplants into discrete segments or flexibly-coupled segments allowsrelative displacement between adjacent segments as needed for theimplant to conform to a curved bone surface contour. An array ofassociated segments can be dimensioned to fit within the requiredperimeter. The segments can be regular geometric shapes or shapes thatare selected as discrete zones of an implant with an irregular roundedshape, that fits the necessary perimeter. The abutting edges between thesegments advantageously can be aligned with changes in the gradient ofcurves of the bone surface contour, such that segments on either side ofthe change lay flat against the bone surface.

FIGS. 3A-3C demonstrate the segmentation of an implant using disc-likesegments that are of regular shape, such as hexagons. In someembodiments discussed below, each hexagon or other segment can be adiscrete separable element, optionally affixed by one of severalalternatives to its adjacent hexagons or other shaped segments. As shownin FIG. 3A, several grouped subsets of hexagons together encompass agiven perimeter shape, in this example a circle. In FIG. 3A, thehexagonal segments 100 are grouped into a central subset 101, two arcs102 that bracket the central subset, and several rim elements 103. Thesegments within each subset can be affixed to one another in a mannerthat allows the segments to flex angularly relative to one another. Inthis embodiment, the grouped-segment subsets are laterally displaceablefor the other subsets. Therefore, individual hexagon segments can flexto conform to a curve, and grouped segment subsets can be moved relativetoward and away from one another. FIG. 3A shows grouped subsets that arelaterally spaced while occupying a plane. FIGS. 3A and 3B demonstratethat by providing one or more tension lines 104 that intersect thesegments or grouped segment subsets, the array is physically tetheredand can be drawn inwardly into lateral abutment by applying tension tothe lines 104 that intersect the segments or their grouped subsets.

In FIGS. 3A and 3B, the implant assumes a relatively rigid shape in aplane due to lateral abutment of tile-like segments 100 in regularpolygonal shapes. In FIG. 3A, plural tile-like segments are coupled intosubsets 101, 102, 103 that form distinct zones of an area to beencompassed. The segments are joined by tension cables 104 extendingthrough holes in the segments and extending between segments,advantageously extending between segments that are members of differentsubsets and zones. As also shown in FIG. 3B, when one or more suchcables is tensioned, gaps between segments are closed. The lateralabutment of the segments in tension provides a structure with somerigidity because the segments 100 are complementary to one another, suchas regular hexagons.

According to one embodiment, an implant as in FIGS. 3A, 3B is assembledfrom repetitive polygon structures for lateral nesting compression intoa solid relatively rigid structure, coupled with arbitrary additionalelements such as perimeter elements that are rounded or otherwiseanatomically shaped for definition of the functional edges, corners andanatomic surfaces that emulate natural cartilage. The embodiments ofFIGS. 3A, 3B illustrate the segments being brought into lateral abutmentin a plane (i.e., a substantially flat shape). By a suitable selectionof lateral relatively displaceable segments and perimeter orarray-internal grouped subsets, the implant can be adapted to a givenarticulating joint and prosthetic restoration, including various curvedsurfaces.

FIGS. 4A through 4C are perspective views of a segmented rigid structurewith cables binding the segments together, resulting in a controllablyflexible construct that can assume a non-planar shape due to theinteraction of the segments and tensioning cables 104. The implant isflexible when the binding cable is not under tension. When tensioned,the flexible rigid segmented structure loses its flexibility due tocable tension causing compressive abutment of the segments. However inthese embodiments, the segments are coupled in that manner that permitsthe implant to assume a nonplanar shape. Specifically, the tension linesinclude at least one outer circuit that, when tensioned sufficiently,pull the segments along the outer circuit up from the plane of segmentsinside the outer circuit.

In FIG. 4A, there are two tensions cable circuits, one surrounding theother. By applying tension to the cables beyond the minimum tension thatbrings segments 100 into lateral abutment, the shape of the implant canbe flexed into a cupped or dished curve. Tension applied specifically tolaterally outer segments surrounding a planar center causes the outersegments to become inclined relative to the planar center. The outersegments can be lifted from the plane of the center and caused tooverlap inner segments, as shown in FIG. 4A. Alternatively, the subsetscan meet at hinging lines that extend across the implant. FIGS. 4B and4C demonstrate drawing an implant into a generally cupped shape byflexing subsets 102 and 103 relative to a planar central subset 101.

In the case of plural outer and inner tension circuits, for example asshown in FIGS. 3A, 3B, tension can be applied to the respective tensioncircuits to differing extents, producing a greater angular deflection inone circuit and less in another. Likewise, the direction of angulardeflection can be varied, for example to configure an implant with aplanar center, and upwardly deflected inner annulus and a downwardlydeflected rim, following an irregular curve of the bone surface andenabling the implant to rest closely against the bone surface. In orderto achieve a curve or to provide a change in deflection from upward todownward, the laterally abutting faces of the segments or subsets can beinclined at an edge plane angle that is other than perpendicular to theplane of the segments or subsets. In that case pulling the segments intoabutment causes the abutting segments or subsets to become relativelyinclined according their edge plane angles.

One advantage of subdividing the implant into relatively movablesegments that can become inclined to one another along hinging lines orthe like is that the implant can be folded or rolled into a smallvolume, introduced into the articulating joint through a small incision,especially using by arthroscopic surgical tools, and opened in place ona prepared bone surface. At that point, tension on cables traversing thesegments is used to draw the implant into a predetermined shape, or atleast to pull the implant down against the surface of the bone byapplying tension between anchoring points.

FIGS. 5A, 5B are illustrations of orthopedic tensioning cables, known inorthopedics as cerclage wiring fixtures and sometimes used to fixtogether fragments of fractured bone. In each case, a loop (shown onlypartly) is formed in a cable of stainless steel or similar cable, withan end drawn through a sliding fitting 105 that can fix the end at apoint along the cable. The cable is looped through or around an anchor(not show) and coupled to the implant. The cable span is shortened andtension is applied by pulling the cable through a sliding fitting 105.In different embodiments that cable is captured by crimping the slidingfitting (FIG. 5A) or by an alternative such as more screws to close aspace traversed by the cable (FIG. 5B), for holding the implant inposition with appropriate tension on the cable.

In the embodiments of FIGS. 3A-B and 4A-C, the segments or subsets ofsegments are physically separate units formed as thin discs. FIGS. 6A-6Cshown an embodiment where the segments 100, again using hexagons as anon-limiting example of a regular polygon shape, are attached to oneanother at arms 107 that span between adjacent segments (see FIG. 6C).The hexagonal bodies of the segments 100 are such that each identicalsegment is defined by an openwork structure of perimeter membersparallel to the plane of an array of segments (FIG. 6A, 6B), standinglegs generally perpendicular to the plane, and structural reinforcingstruts extending diagonally.

The reinforced segment bodies are relatively rigid, but the connectingarms 107 extending between segments are relatively more flexible,allowing an array of such connected segments to form a mat or sheet asseen in FIG. 6C, which can be conformed to a curved boned surface andattached by fasteners. The openwork structure enables fasteners such assurgical staples to be passed through the segments at strategic pointsinto underlying bone tissue. The openwork structure also advantageouslycan be part of a composite molded structure wherein a hydrogel sheet ismolded over the segments. The segments are spaced below an exposedhydrogel surface that forms a lubricious sliding surface of the implant.The implant is supported internally by the segments and can be attachedto the bone surface by fasteners passed through the segments into thebone.

In FIGS. 6A-6C the basic polygon shaped segment 100 can be made in adigital accumulation technique (3-D printing) in a metal or metal alloycomprising Ti (titanium) or Ta (tantalum), or in a polymer such as PEEK(polyetheretherketone) or a similar material for the basic polygonsegment, which provided structural support. In one embodiment thesegment comprises 0.25 mm diameter struts configured to define thesegment, and having internal struts to provide a substantially rigidstructure. The polygon segments are relatively rigid and incompressibletiles. The array of Polygons is flexible as shown in FIG. 6C. Howeverwhen supplemented by one or more tension lines such as a Ti cable wovenor sewn through individual polygons along an anchoring line or in acircuit, tension applied to the cable passing through the individualpolygons can be arranged to pull the polygons laterally against oneanother, making the array substantially more rigid as installed.

FIGS. 7A through 12 illustrate embodiments wherein segments that arediscrete separate elements are mechanically attachable to the adjacentsegments in an array, via complementary hinging structures that areprovided on the edges of the segments, again represented as regularhexagon shapes as a nonlimiting example of a regular polygon. In FIGS.7A-C, each segment 101 has an openwork structure of elongated membersforming perimeter sections, standing legs and reinforcing struts. Inthis embodiment, each diametrically opposite side has either one centralhinge knuckle 112 or two straddling hinge knuckles 113, that allowadjacent segments 101 to fit with one another in a sheet array as shownin FIG. 8. The hinge knuckles 112, 113 are cannulated or formed withbores 114, running both parallel to the associated edge of the segmentand perpendicular to the associated edge. A tensioning cable 104 (notshown in FIGS. 7A-7C) can be passed through the aligned bores in thehinge knuckles 112, 113 of adjacent segments, functioning as a form ofhinge pin. Additionally, tensioning cables can be passed perpendicularto the bores in the hinge knuckles, through the centers of adjacentsegments.

FIGS. 7B, 7C illustrate that the underside of the segments, namely theside that will rest against a bone surface, is not flat but has aplurality of downwardly protruding points 115. The points are configuredto bear against bone tissue underlying the implant, and can betteraccommodate surface irregularities than an alternative segment having aflat bottom surface.

FIG. 8 is a plan view showing an array of segments that are at leasttemporarily attached to their adjacent segments by fitting together thehinge knuckles 112, 113 of adjacent segments. In this arrangement, atension cable passed along a line through the cannulae of adjacentsegments serves to define a hinging axis. A tension cable can be passedthrough the co-linear aligned cannulae of every second segment in thearray, namely through the hinge knuckles and parallel to the sides ofthe segments. Or a tension cable can be passed through each adjacentsegment in a line of segments, oriented perpendicular to the segmentsides. In each case, these tension cable routes, as well as other routesand tension cable circuits, are useful to anchor the implant whileenabling the implant to flex into a various potentially curving orangularly diverse shapes. In FIG. 9, the dashed lines show the potentialroutes of a tension cable through a segment, parallel or perpendicularto the segment sides. In an alternative embodiment (not shown Fig.), theremaining reinforcing struts shown in FIG. 9 without dashed lines, canalso be cannulated to provide additional cable paths.

The embodiment of FIG. 8 can also comprise tile-like substantially rigid3-D printed Metal, Ti, Ta or PEEK or other polymer polygon elements. Thesegments have cannulae 114 engineered into the structure to facilitateand guide cables coupling the array into a flexible array of individualrigid polygons. The array becomes rigid as the cables are tensioned andthen crimped in tension as well as anchored. Along the edges where thecannulae of adjacent hinge knuckles are nested and in co-linearalignment, the tension line passing through the aligned cannulae ofadjacent elements also defines a hinge axis. Tension applied by atension line coupled between spaced points draws together the elementsthat are disposed along the tension line.

FIGS. 10A and 10B show and alternative and somewhat simplifiedembodiment of a regular polygon segment 101 with hinge knuckles andcannulae 114 aligned as shown in dotted lines in FIG. 9. The segment inthis embodiment is one thickness of elongated members, but additionallyhas a central opening 117 that is useful for tension cable passage andfor receiving fasteners such as surgical staples. This embodiment canlikewise be made in 3-D printed Metal, Ti, Ta, PEEK or other polymer.

In FIG. 11, an array of simplified regular polygon segments is showntraversed by a tension cable defining a circuit through the cannulae ofthe segments located around the perimeter of the implant. With tensionapplied to the cable around the circuit, the perimeter segments aredrawn inwardly against the segments occupied within the perimeter orcircuit. This adds rigidity to the array of segments.

A circuit as in FIG. 11 can also be configured as in FIG. 12 to engagewith external fasteners (not shown) at points along the circuit. In FIG.12, depending loops 117 can attach to anchoring staples, screws, plugsor the like. The loops 117 can be located at any of the traversedsegments of the array, and thus the locations can be chosen tocomplement the anatomy at the recipient site, the specific shape andlocation of the implant and similar biomechanical demands in specificapplications.

The aspect of the segments being tensions laterally against one anotherprovides for the possibility of using inclined abutting surfaces toproduce simple or complex curves in one or two planes, across an arrayof segments. FIG. 13 shows that inclined lateral faces forming chamferededges on one or both of two segments that are urged against one anothercause the abutting segments to diverge angularly from the common planethat they might assume if the abutting faces were parallel as in FIG.15. Successive segments can be formed with similarly inclined side facesto follow a simple curve. By selectively interspersing sequences ofplural segments with side face chambers in opposite directions, acomplex curve is provided with S-shaped segments curving in oppositedirections as illustrated in FIG. 14.

In FIGS. 13, 14, the end faces of disc-shaped segments are integrallyformed with a chamfer or tilt relative to a plane perpendicular to theadjacent top and bottom faces, which in this example are parallel. FIG.16 demonstrates that the chamfer or tilt required to achieve the sameresult can be obtained by inserts interspersing one or more insertelements 118 between otherwise unchamfered segments. Two mirror imageinserts 118 are shown in FIG. 16. Use of one such insert would halve theangular diversion achieved. As seen in FIG. 17, similar inserts can beprovided with complementary structures for locking the adjacent insertsinto a predetermined alignment when urged together (in this example theabutting inserts being held in coplanar position).

The illustrated structures are 3-D modeled, enabling creation of precisegeometries for the desired curvatures, which can be produced directlyusing 3-D printing lasers for precision fabrication, alone or togetherwith laser or e-beam sintering of Metal, Ti, Ta, PEEK or other polymerso as to provide a desired surface configuration, or other appropriatemanufacturing methods not limited to 3-D printing. The segments can becut from a fabricated whole, or 3-D printed as individual segmentsassembled into a whole. Either way the segments, either cut orindividually 3-D printed are engineered to restore the desiredfunctional geometry as the threaded cable is tensioned compressing thesegments into a relatively rigid structure as a whole.

The segmented implant structures disclosed herein can be advantageouslyformed by digital additive manufacturing techniques, i.e., 3-D printingdirectly into an array of segments. The implant is that case is 3-Dprinted as a whole, in the final anatomic shape required. Implants canbe 3-D printed and then separated into segments that are supported withtension cables as discussed above. The segments can engineered andprinted separately to fit together to form a flat array or a shapedstructure that is complementary to an anatomical surface. Formation by3-D printing enables the segments to be defined as individuallycustomized segments, but 3-D printed as an assembled group. The groupcan include structures that engage between adjacent segments orstructures that flexibly span between adjacent segments.

The implant segments as discussed herein are useful as the structuralsupport within a composite molded construction that is attached to asurface of one bone in an articulating joint and carries a hydrogellayer with a lubricious sliding surface presented on a side facing anopposed bone in an articulating joint. In the embodiments of FIGS. 7Cand 10B, for example, structures on the anchoring side of the implantinclude points that help to stabilize the position of the implant on theanchoring side (opposite from the hydrogel side). In anotheradvantageous aspect, the anchoring side of the implant can be structuredas a trabecular surface adapted to facilitate tissue ingrowth. Images of3D-printed, FDA-approved trabecular metal available for commercial usein total joint replacements, are shown in FIGS. 18A, B and C. Thespecific pore size (C) can be selected to optimize bone tissue healingwhile facilitating hydrogel adhesion.

FIGS. 19A, 19B and 19C illustrate a polygonal segment 101 with cannulaethrough the center of the segment, and protruding points similar tothose of FIGS. 7C and 10B. In the embodiment of FIGS. 19A, B, C, theunderside of the segment (namely the side to be anchored against bone)has a relatively wide and flat annular area that can rest against thesurface of the anchor bone. This annular area is advantageously formedof or coated with a trabecular metal layer for boney ingrowth. Thisembodiment has a relatively low profile and as shown in FIG. 19C has acentral cavity on the underside providing access to any tensioning cablethat traverses the segment through the cannulae provided. Thisembodiment is also preferably produced by digital additive techniques(3-D printing) in metal TI, Ta, PEEK or other polymer.

FIGS. 20A-D illustrate variations of cold pressed woven Metal, Ti or Tawire, PEEK, or polymer mesh sheets, carrying polygonal areas adapted tobe molded together with hydrogel to provide a composite structure thatexposes a lubricious sliding surface to the articulating joint andfacilitates attachment to and ingrowth with bone tissue on the bone towhich the implant is mounted. When sandwiched together, the undersidehas a tightly woven mesh pressed against the bone surface layer,sintered, sewn or welded together into a quilted woven or unwoven battmesh with lofted zones that function in a manner similar to theforegoing polygonal segments. The quilted pads or lofts facilitatehydrogel or polymer permeation to improve the sliding surface, andbonding to the woven or unwoven mesh for bone adhesion and optimallongevity of this construct.

FIGS. 21A-C show a quilted woven pad (A), with a quilted structure toprovide loft for hydrogel permeation, compression and tissue in-growth;a close up of a quilted structure loft (B); and a cross-section throughloft of quilted woven structure (C).

FIG. 22A shows a perspective view of the quilted-pad arrangement ofsandwiched Metal, Ti, Ta, PEEK or other polymer mesh quilted material,preferable a loft or thickness equivalent to three to five times thefiber diameter to promote polymer (108) permeation and adhesion. FIG.22B is a side section showing the quilted pads forming the underside ofa composite with hydrogel occupying the upper side.

FIG. 23A shows a suture cable grid that is incorporated into the implantstructure as shown in FIG. 23B prior to hydrogel composite molding. FIG.23C show the grid including in the composite, namely between thesandwiched mesh quilt sheets. The suture cable grid spreads compressiveforces urging the implant against the underlying bone surface whensutures or anchoring cables are affixed to apply tension pullingattachment points (shown as optional circles in the suture grid) awayfrom one another and so as to wrap over bone condoyles or the like. Thisarrangement confines stresses to the suture grid, protecting thehydrogel interface and underlying bone ingrowth surface, whileeffectively compressing the quilted mesh against the bone implantinterface.

In FIG. 24A, a cannulated segment array is coupled to a woven Ti or Tamesh sheet, creating a quilted mesh for permeation of hydrogel on oneside and for adhesion of the quilted mesh to bone on the other side. Itshould be understood that the term “mesh” includes woven, knitted orunwoven batt structures. In FIGS. 24B, C, D and E, the segments carryquilted tops that appear as domes or bubbles into which the hydrogel ispermeated.

In FIGS. 25A through D, an alternative embodiment of segment 101 isshown that has a structure similar to that of FIG. 19 but with an addedupper annular ring 121 and an array of macropores 122 just below theannular ring. This segment can likewise comprise a 3-D printed Metal Ti,Ta, PEEK or other polymer polygonal segment. The macropores admithydrogel permeation and adhesion between the segments and the hydrogel.As in the embodiment of FIG. 19, tension cable holes open on the sideface for receiving tension cables that traverse the segment. A centralopening on the underside provides access to the cable traverse. Theunderside of the segment has position stabilizing points and a flatannular area that can have a trabecular structure or coating. FIGS. 26Aand B respectively show an array of these segments from below and fromabove. FIG. 26C is a cross section through a portion of the segmentarray. FIG. 26D shows a composite molding in which hydrogel occupies thetop surface layer.

By digital additive manufacturing techniques (3-D printing), it ispossible to produce an array of segments that are resiliently attachedto one another as a result of the structures provided by the printingprocess. FIG. 27A illustrates an alternative embodiment of a polygonalsegment 101 wherein arching struts 124 protrude radially from thesegment. The array is printed as a unit with plural segments so formed,as shown in FIG. 27B. The arching struts of each segment are dimensionedwhen printed to extend over its adjacent segments at each polygonalside. Among other advantages, this resiliently attaches the adjacentsegments of an array while permitting some freedom for relativedisplacement and angular diversion whereby the array can conform to acurved bone surface. Additionally, the cascade of arched struts fromboth polygonal sides at each abutment interleave with one another asshown in FIG. 27C in plan view and 27D in sectional view, providing afibrous thickness at which hydrogel in the composite molding, shown insection in FIG. 27E, is fixed securely to the segmented anchoring systemby the arching struts that become embedded in the hydrogel.

The cascading interleaved arching struts bridge across adjacentsegments, creating a hinge between the rigid segments, in this case, forexample, hexagons. The particular architecture of the 3-D printedstructures including the arching struts can be defined by currentdigital additive manufacturing software to optimize for porosity,integral strut strength, and generally to provide a material modulus ofelasticity gradient from the relatively rigid bone to the relativelyflexible hydrogel.

As in the other embodiments, the anchoring underside of the segment cancomprise or have an applied layer of trabecular Metal, Ti or Ta in abase that is relatively rigid, but carries an arcade of arching strutsof a relative resilient material, especially comprising a less rigidPEEK or polymer arcade that is 3-D printed onto the metal base. In oneembodiment, the arching struts are configured to emulate the tissuestiffness gradient present in a normal synovial joint at the hyalinecartilage to bone interface, namely quite stiff near the bone andprogressively softer leading out toward the hydrogel sliding surface.

A substantially continuous foil of metal such as tantalum (Ta) ortitanium (Ti) foil, or PEEK or other polymer membrane, can orient andsecure multiple rigid polygonal segments of a flexible anchoring systemand yet permit deformation of the foil as needed to flex, roll or foldthe implant anchoring system, for delivery into the joint through asmall incision, and also deformation of the foil by relativedisplacement of rigid segments affixed to the foil. Such an embodimentis shown in FIGS. 28A and B with segments 101 shown affixed to thesurface of the foil sheet 126 in FIG. 29A. In FIG. 29B, hydrogel ismolded atop the segments, permeating down to the foil layer, which stopspermeation below that.

A flexible cable is strategically threaded through the rigid segments tocouple the rigid segments into a construct, that can be tensioned into arigid anchoring system with a pre-determined specific joint surfacegeometry for bone articular surface compression and fixation within asynovial joint. This design is disclosed as a flexible sandwichedhoneycomb structure with the material property performance benefitsassociated with this structural design, with the additional benefit offlexibility for delivery into a restrictive space for the device'sultimate functional intent.

A metal, Ta, Ti foil, PEEK or other polymer membrane 126 as shown inFIG. 29A can serve as a support for 3-D printed trabecular anchorsegments. The foil membrane holds the segments together, duringproduction processes including, 3D Printing, segment cutting, threadingcable, molding polymer bearing surface processes, packaging andsterilization. The foil membrane is flexible, permitting the constructto be flexed during delivery into the joint. Holes through the foil inthe area of the peripheral sections can receive screw, staple or tackfixation which could be used alone or with additional provisions tolocate the implant correctly and to secure the implant anchor to bone. Atension cable is laced through the segments such that when the cable istensioned the segments get compressed into a rigid construct compressedagainst the bone recipient site.

FIGS. 30A through F show an embodiment with a segmented anchoring systemheld together with a layer of Metal, Ta, Ti foil, PEEK or other polymermembrane integral to the anchoring segments on the hydrogel side,holding the anchor segments aligned in the desired configuration forfixation of the implant. The foil is flexible, permitting deformationsufficient for delivery of the implants through a small incision (e.g.,by arthroscopic access). The foil is unrolled and spread out in place,which restores the 3D structure and allows the implant to fit againstand conform to the boney surface of the recipient site. Foil canfunction as a base layer on which the trabecular base layer is thenprinted, preferably with a porosity on the bone side adapted for bonetissue healing. The opposite side of the foil can serve as the base forthe hydrogel bonding layer with a graduated stiffness reduction toaccommodate the more compliant hydrogel, minimizing the modulus ofelasticity mis-match. The foil overlying the hexagon structured layercreates a flexible sandwich honeycomb structure well known for itsstructural lightweight strength.

FIGS. 31A-D show juxtaposed implant and anchoring structures 131. InFIG. 31A, the anchoring structures 131 comprise driven nail-likeelements or screws with eyelet heads, to be embedded in bone (not shown)around the periphery of the site at which the implant is to be attached,such as the top of the tibia. The anchors can comprise cerclage typecrimping fittings at the eyelet heads such that one or more tensioncables can be drawn through the eyelet and permanently fixed by crimpingthe eyelet. (See also FIGS. 5A, 5B.)

As shown in FIGS. 32-34, one or more tension cables 104 can be sewn orguided through the segments 101 in an array, along paths chosen so thattension draws the segments 101 laterally together. In FIG. 32, thearrangement of tension cables is bilaterally symmetrical and proceedsfrom anchoring staples 135 or from segments 101 affixed to the bone byanchoring staples 135.

In the embodiments of FIGS. 32-34, the segments are openwork hexagonsegments with strut members, e.g., sized about 3-5 mm face strutdimension. This form of segment is apt to receive a staple, for exampleas shown in FIG. 33, because the legs of a staple can pass throughspaces between the segment struts and securely engage the segment. Asshown in FIGS. 33, 34, a staple can be preliminarily inserted into asegment and carried there awaiting deployment, at a position that doesnot protrude below the segment. When affixing the implant, the surgeonpartially retracts the staple and tilts the staple up relative to theunderlying bone surface. The staple then is driven down into the bone toaffix that point in the array. The driven staple and/or its associatedsegment are then available as fixed anchoring points. Tension on thecable pulls other segments laterally toward the fixed anchoring points,stiffening the array by lateral abutment and compression of thesegments, whereupon other points can be anchored in turn.

According to the embodiments disclosed herein, implants can compriseseparated or laterally-attached segments that provide a downward boneinterface by trabecular material or a fibrous woven or unwoven mesh, andare molded in a composite structure with a hydrogel surface layer. Thelateral attachment can comprise a sheet or foil that carries thesegments into position as well as providing a barrier to preventpermeation of the hydrogel into the fibrous or trabecular layer on theunderside.

Trabecular Bone interface struts thickened for optimal pore size fortissue healing, while accommodating cables, cannulae, staple slot andstaples (see below). For intrusion or permeation of hydrogel into thesegments, in the foregoing embodiments, a fibrous mesh or batt underliesthe segments to form a permeation barrier at the underside (the boneaffixation side). The hydrogel is molded into a perforated or fibrousstructure for secure attachment of the hydrogel to the segments, such asa dome with lateral macropores or an array of arching struts. A smoothanchor-bearing surface interface can be provided with bearing surfaceon-lay.

The paths traversed by tension cables are arranged with clearance andseparation so that multiple cables can pass thru single polygon segmentswhen necessary. Cannulae and/or dividers prevent cable overlap andbinding by providing a defined path.

The perimeter polygons will be anatomic joint implant specific withmodified outside edges “rounded” to minimize stress at the gel-polygoninterface at corner edges and to facilitate outer edge adhesion ofhydrogel for implant edge coverage.

At least certain ones of the perimeter polygons in an array preferablyare securely compressed to the subchondral bone surface along entiremargin of implant. This may be facilitated, for example, using boneanchors that engage with perimeter polygons or are a least locatedclosely adjacent to the perimeter polygons. The perimeter polygonsselected for anchoring can be at regularly spaced points, at apices ofan array or otherwise strategically placed to maximize compression ofthe array against the subchondral bone tissue (including but not limitedto any anchor polygons that are affected by a nearby orpolygon-traversing bone anchor).

Rim/Perimeter Anchor Polygons preferably meet some or all of the abovedesign criteria. In addition, Anchor Polygons can be particularlyconfigured to accommodate the cable stress loads through cannulae orplate partitions controlling the path of cable to and/or from a boneAnchor.

Staple Anchor Polygons accommodate the cable and define staple slots orpaths by which a staple or similar fastener can pin one or more anchorpolygons to the subchondral bone tissue. One option is to supply orpackage the Staple in a semi-retracted “Neutral” slot position at whichthe Staple is poised to be driven for delivery into the bone of thejoint, e.g., by applying manual force using a tool. The staple can beengaged into a “deployed” slot position once the array of elements ispositioned on the joint surface, over a prepared area including Staplebone entry sites. Staples can be manipulated (moved, set, retracted,etc.) with an Arthroscopic suture grabber by catching an edge of astaple (or a cable loop) and pushing/pulling backwards. Manipulation canbe used to move the staple back in the “Neutral” slot and for leveringthe back edge of Staple up until it securely engages the “Deployed”slot, aligning staple prong tips into subchondral bone while the body ofthe staple engages in the array element. “Neutral” and “Deployed” slotscan be provided at a 45-60° angle to each other. The staple is driveninto & below subchondral bone, along the deployed slot until locked intoplace. The staple final locked position couples the segment/polygon andthe staple as a solid unit engaging the subchondral articular surfaceunder wedge compression and cable tension.

The following outline details surgical steps in installing an implant asdescribed:

I. Prepare Recipient Site

-   -   A. Size/Template & Mark Recipient Site    -   B. Debride/Remove residual Cartilage    -   C. Contour Recipient Site Bone Surface    -   D. Template & Mark Staple Recipient Sites

II. Align Staple Anchor Fixation Sites

-   -   A. Adjust Implant Trial Staple Recipient Sites    -   B. Prepare Aligned Staple Anchoring Sites    -   C. Install Screws if Screw Anchor Utilized    -   D. Evacuate All Joint Debris

III. Install & Secure Implant

-   -   A. Deliver Implant into Joint (Compressive Cannula)    -   B. Adjust Implant Rim Position & Staple Alignment    -   C. Align & Deploy “Remote” Posterior Staple Anchors    -   D. Secure, Tighten & Lock “Remote” Posterior Anchors & Tension        Cable    -   E. Align & Deploy “Near” Anterior Staple Anchors    -   F. Secure, Tighten & Lock “Near” Anterior Anchors & Tension        Cable    -   G. Tighten & Lock Cable Tension    -   H. Evacuate All Joint Debris

Short and long-term clinical design considerations are to achieve goalsincluding a) pain relief; b) restoration of patient function; c) minimalmorbidity; d) stable fixation to permit tissue ingrowth; e) Rigidfixation necessary for bone ingrowth; e) Stable, less rigid, fixationnecessary for fibrous tissue ingrowth; f) Device material properties attissue implant interface must reflect rigidity demands of recipient siteand desired tissue ingrowth.

As described herein, an implant for emulating hyaline cartilage in anarticulating mammalian joint includes an array of laterally adjacentsegments encompassing an area of a surface corresponding to the hyalinecartilage, and a hydrogel layer affixed to at least on one side of theimplant, configured to provide an exposed sliding surface in thearticulating joint. Specifically, the segments are movable relative toone another to a limited extent enabling segments in the array todiverge from one another and to conform to a topography to which theimplant is to be attached.

The segments are relatively displaceable in at least one of lateralinter-spacing and inclination relative to one another so as to divergefrom a direct abutment in a common plane. In certain embodiments, thesegments define cannulae through which at least one line can be passedto couple adjacent ones of at least a subset of the segments. Inadditional embodiments, a mechanically attached subset of adjacent onesof the segments are configured to hinge relative to one another on atleast one axis defined by cannulae through which the line passes.

Advantageously, the segments define aligned cannulae along a pluralityof parallel lines through which a tension line can be passed defininghinge axes. For cinching together adjacent segments in at least a subsetof the array, an outer one of the plural tension lines surrounds aninner one of the tension lines, and the outer and inner ones of thetension lines are tensioned separately whereby a complex curved shapecan be assumed.

In some embodiments, the segments comprise regular polygon shapes havingcomplementary hinge forming edge structures at which adjacent segmentshingeably engage. These can have cannulated hinge knuckles, archingstruts and other shapes that engage discrete segments. Alternatively oradditionally, the segments can be affixed to a backer sheet of fiber orfoil that provides a barrier to hydrogel permeation in a compositemolding, or can carry a trabecular or similar material configured fortissue ingrowth.

Certain embodiments of the segments are structured to admit a fastenerfor affixing selected ones of the segments to underlying tissue. Forexample, segments comprising vertical, horizontal and inclined framemembers can receive staples or similar fasteners configured to extendbetween spaced ones of the frame members for affixing the segment to abone underlayment.

The invention having been disclosed in connection with several examplesand illustrative embodiments, it should be noted that the invention isnot limited to the embodiments used as examples, and is capable of otherembodiments within the scope of the appended claims defining the scopeof the invention in which exclusive rights are claimed.

1. An implant for emulating hyaline cartilage in an articulating mammalian joint, comprising: an array of laterally adjacent segments encompassing an area of a surface corresponding to the hyaline cartilage; a hydrogel layer affixed to at least on one side of the implant, configured to provide an exposed sliding surface in the articulating joint; wherein the segments are movable relative to one another to a limited extent enabling the array to diverge from and also to conform to a topography.
 2. The implant of claim 1, wherein the segments are displaceable in at least one of lateral inter-spacing and inclination relative to one another.
 3. The implant of claim 2, wherein the segments define cannulae and further comprising at least one line passing through the cannulae of adjacent ones of at least a subset of the segments.
 4. The implant of claim 3, wherein at least a mechanically attached subset of adjacent ones of the segments are configured to hinge relative to one another on at least one axis defined by cannulae through which the line passes.
 5. The implant of claim 2, wherein the segments define aligned cannulae along a plurality of parallel lines and further comprising at least one line passing through the cannulae and defining hinge axes.
 6. The implant of claim 3, comprising a plurality of lines passing through the cannulae of adjacent ones of a tethered subset of the segments, and wherein an outer one of the lines surrounds an inner one of the lines and the outer and inner ones of the lines are tensioned separately.
 7. The implant of claim 1, wherein the segments comprise regular polygon shapes having complementary hinge forming edge structures at which adjacent segments hingeably engage.
 8. The implant of claim 7, wherein the hinge forming edge structures are cannulated along at least one of an axis of hingeable engagement and an axis extending through an associated one of the regular polygon shapes.
 9. The implant of claim 1, wherein the segments include a backer layer configured for tissue ingrowth.
 10. The implant of claim 1, wherein the segments are structured to admit a fastener for affixing selected ones of the segments to underlying tissue.
 11. The implant of claim 10, wherein the segments comprise vertical, horizontal and inclined frame member, and wherein at least one said fastener is configured to extend between spaced ones of the frame members.
 12. The implant of claim 11, wherein the fastener comprises a staple and is configured for selective placement at one of at least two different angles relative to the frame members.
 13. The implant of claim 12, wherein the staple is configured to extend through the frame members at a selected on of at least two angles relative to an underlying surface.
 14. The implant of claim 11, wherein at least one of the frame members and the fastener is configured for attachment of a suture
 15. The implant of claim 1, wherein at least one of the laterally adjacent segments and subsets of the laterally adjacent segments are displaceable relative to one another at lines of abutment.
 16. The implant of claim 15, wherein said at least one of the laterally adjacent segments and subsets of the laterally adjacent segments are configured to diverge angularly along the lines of abutment, whereby the implant can conform to a surface that has a changing gradient across the lines of abutment. 